 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include <ctype.h>
 #include <math.h>

 int main(int argc, char **argv) {
     
	int sum = 0, a, b, temp, flag = 0;
	 	
	for ( int i = 1; i < argc; i++) 
	{
		sscanf(argv[i], "%d", &a);
		temp = a;
			for (int j = 0; j < (strlen(argv[i])); j++)
			{		 
				b = a%10;
				a = a / 10;
				sum += b*pow(10,(strlen(argv[i]) - 1-j));
				/* printf(" a - '%d' \n", a);
				printf(" b - '%d' \n", b);
				printf(" sum - '%d' \n", sum); */
			
				if( !isdigit(argv[i][j]) ){
					j = (strlen(argv[i]) - 1);
					flag = 1;
				} 
			}
			
		if ( i == argc - 1  && flag == 1)
		{
			printf("Usage: numbers\n");
		}
	} 
	
	if( argc == 1 && flag == 0 ) 
	{
		printf("Usage: numbers\n");
		return 0;
	}  
	
	if ( flag == 0){
		//printf("%d\n", sum);
		
		if ( sum == temp )
		{
			printf("yes\n");
		}
		else
		{
			printf("no\n");
		}
	}
   
    return 0;
 }